Looks good. Looks very similar as to how Gearotic does it, a digital subtraction where the involute evolves from the instantaneous rate of change during its construction?

Right now, these curves are generated without any subtraction at all, just solving differential equations numerically in 2 dimensions. This produces "pure" involute curves that are exactly correct at every point. The only problem is that since these curves evolve, they may interfere with each other as they engage or disengage, so my last task is to find an appropriate solution to minimally clip, truncate or sheer off areas to prevent the teeth from jamming - that final piece may be done via a subtraction algorithm, but we'll see.